1. Field of the Invention
The present invention relates to an optical information recording and reproducing apparatus which comprises a light source for generating recording light and a light source for generating reproducing light, which are different from each other, and in which a quantity of shift or offset of servo conditions on the basis of both of the lights is dissolved so that the reproducing light is used to perform the servo control at a recording mode.
2. Related Art
In an optical information recording and reproducing apparatus in which information is optically recorded and reproduced with respect to an optical recording medium such as an optical card or the like, a light source for generating recording light and a light source for generating reproducing light are separately provided, and an optical information recording and reproducing apparatus of a two-light-source system has been proposed in which verifying operation is performed which confirms recorded information by a reproducing light spot immediately after recording to increase effective recording speed, as an arrangement in which a single track is illuminated by two optical spots including a recording light spot and a reproducing light spot to simultaneously perform recording and reproducing.
As the optical information recording and reproducing apparatus of the two-light-source system, there are a prior art disclosed in Japanese Patent Laid-Open No. HEI 2-61830 (61830/1990) and a related technical art example disclosed in Japanese Patent Laid-Open No. HEI 4-82028 (82028/1992), for example.
Any one of these optical information recording and reproducing apparatuses is so arranged as to perform track control and focus control by the reproducing light. Further, in a photo detector for detecting a reproducing signal, a focus detecting signal and a track detecting signal on the basis of a change or variation In the reproducing light, the photo detector is so arranged as not to receive the recording light.
For example, an optical system 150 of the apparatus disclosed in Japanese Patent Laid-Open No. HEI 2-61830 (61830/1990), as shown in FIG. 1 of the attached drawings, is arranged as follows. That is, a polarizing direction is set such that recording light is generated from a recording light source 151, and the recording light reflected by an optical card 164 is transmitted through a reflecting surface of a polarization beam splitter 157. Accordingly, the recording light is not incident upon a pair of photo detectors 153 and 154.
That is, the recording light generated from the semiconductor laser 151 is brought substantially to elliptic parallel light by a collimating lens 155. After only a minor-axis direction of the ellipse is enlarged by a shaping prism 156 so that the parallel light is shaped substantially to a circular form, and is incident upon the reflecting surface of the polarization beam splitter 157 substantially at P-polarization. Accordingly, almost all of the parallel light is transmitted so that the parallel light proceeds on an optical axis of an objective lens 158 on a center of a beam. The parallel light is condensed onto the optical card 164 so that an optical spot of the recording light is formed. Light reflected from the optical card 164 is returned to a direction opposite to the incidence. That is, the light is condensed by the objective lens 158, is transmitted through the polarization beam splitter 157, and is returned to the side of the shaping prism 156.
On the other hand, reproducing light generated from an end-face light emitting diode 152 which is brought to a reproducing light source is brought to parallel light by a collimating lens 159. The parallel light is such that only an S-polarization component is reflected by the polarization beam splitter 157. The reflected light is incident upon a position which is out of the optical axis of the objective lens 158, and is converged or condensed onto the optical card 164 to focus into a slit-like image as an image on a light emitting surface of the end-face light emitting diode 152. The light reflected by the optical card 164 passes through the objective lens 158, and is reflected by the polarization beam splitter 157. Subsequently, the light passes through a mirror 160, an imaging lens 161 and a mirror 162, and is guided to a half mirror 163. A part of the light is transmitted through the half mirror 163, and reaches one of the photo detectors 153. The remaining part of the light is reflected by the half mirror 163, and reaches the other photo detector 154.
Further, an optical system 170 of the apparatus disclosed in Japanese Patent Laid-Open No. HEI 4-82028 (82028/1992) and illustrated in FIG. 2 is arranged as follows. That is, recording light generated from a recording light source 172 and reproducing light generated from a reproducing light source 171 are differentiated in wavelength from each other. Although the recording light and the reproducing light reflected by an optical card 164 are incident upon a toric lens 192 for focus detection, only the reproducing light is transmitted through a dielectric multi-layer film or membrane having wavelength selection permeability formed on a lens surface, and the recording light is reflected. Accordingly, the recording light is not incident upon a photo detector 173.
The recording light having wavelength of 830 nm generated by the recording light source 172 is differentiated in wavelength from the reproducing light having wavelength of 780 nm generated by the reproducing light source 171. The recording light and the reproducing light are modified or corrected respectively to parallel lights by collimate lenses 174 and 191. The reproducing light is further divided into three lights (0 (zero)-order light and .+-. primary diffracted lights) by a diffraction grating 175, which are incident upon a dichroic prism 176.
The recording light and the reproducing light which are composed by the dichroic prism 176 are shaped by a shaping prism 177 and, subsequently, are transmitted through a polarization beam splitter 178. The recording light and the reproducing light are converted to circular polarization of light by a 1/4-wavelength plate 179 and are focused by an objective lens 190 to form respective optical spots on the optical card 164. The recording light and the reproducing light are reflected by the optical card 164 and, subsequently, are transmitted through the objective lens 190 in an opposite direction. The recording light and the reproducing light are brought respectively to lights by the 1/4-wavelength plate 179, in which a polarization direction is rotated through 90.degree. with respect to the incident time. The lights are reflected by the polarization beam splitter 178 and are incident upon the toric lens 192 for focus detection.
However, the arrangement is as follows. That is, since the dielectric multi-layer membrane of wavelength selection transparency is formed on the surface of the lens 192, only the reproducing light having the wavelength of 780 nm is transmitted, and the recording light having the wavelength of 830 nm is reflected. Accordingly, the recording light is not incident upon the detector 173.
Accordingly, the optical information recording and reproducing apparatus such as the prior art which is separately provided with the light source for generating the recording light and the light source for generating the reproducing light is arranged such that the recording light is not received by the photo detector. Thus, there is no necessity of the recording light other than the time of recording operation, and the recording light is not irradiated on an optical recording medium other than the time of recording operation.
The following problems are considered in such optical information recording and reproducing apparatuses.
1. In the prior art or the like, since the semiconductor laser 151 or the like for emitting the recording light upon the time of recording operation which performs recording of information onto the optical recording medium is brought to a light-emitting condition, transient affection or influence of light emission characteristic of the semiconductor laser 151 is apt to be come under during a period of time in the vicinity of start of the recording operation so that formation of a uniform pit becomes difficult. PA0 2. In the arrangement of the prior art example or the like, the recording light is arranged so as not to be detected by the photo detector, and the focus control is performed only by the reproducing light. Accordingly, if optical regulating shift or offset is generated by a change with the passage of time and a temperature change, the recording optical spot is brought to a focus shift or offset condition. Thus, the possibility is generated in which it is impossible to accurately record information to be recorded. PA0 3. In the arrangement of the prior art example or the like, there is a possibility that recording of the information is performed under a condition of tracking offset in which the recording light spot is offset from a central position in a width of each of the tracks. In this case, in a case where the recorded information is reproduced, it becomes difficult to surely detect the pit. Thus, it is expected that probability of generation of an error of reading increases.
That is, since the size of the optical spot increases under a defocus condition, an energy density thereof decreases (less than a case of a focus condition). Thus, there is possibility that the pit cannot surely be formed.